ISUAL Imager Stewart Harris

Outline Imager technical objectives Detector design and specification CCD clocking and readout Mechanical layout / detailed description Electronic design and interface Functional parameters NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Imager Objectives Provide high temporal and spatial resolution imaging of Sprites and other emissions related to lightning storms Provide imaging of aurora and airglow NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Imager Optical Path Optics Detector NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Optical Specifications Filters 1: 670 - 750 nm 2: 762 nm 3: 427.8 nm 4: 630 nm 5: 557.7 nm 6: 732 nm NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Optical Specifications, con’t. Lens Focal length: 62.5 mm Focal ratio: f/1.56 Image format: 25 mm diagonal Spectral band: 420 - 780 nm NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Detector specifications Image Intensifier Type: 25 mm Gen II Manufacturer: DEP Photocathode: Super S25, 6 mm quartz window MCP: Single, 100 ns gating Phosphor: P46, fiber optic window 2 µs decay time constant Fiber Optic Taper Input diameter 25 mm Output diameter 14 mm Ratio 1.8 : 1 NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Detector specifications, con’t. CCD Type: 1024 x 1024, frame transfer Manufacturer: Dalsa, IA-D4 Antiblooming: Vertical anti-blooming (VAB) Primary mode: 512 x 80 (binned 2x2 and masked) Pixel size (unbinned): 12 µm x 12 µm Pixel size (binned): 24 µm x 24 µm # of Outputs: 2 Pixel readout rate: 8 MHz NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

CCD Block Diagram IA-D4 Image Sensor Image Area Output Storage Area NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

CCD Active Area Masking Imaging Earth Limb Narrow, 6:1 Aspect Ratio CCD Active Area Mask applied to f/o window Size: 1024 x 170 (unbinned) Size: 512 x 85 (binned) FOV: 20° x 3º Top view of Dalsa CCD with f/o window NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

CCD Camera Imaging Modes Sprite Burst Mode Sprite Continuous Mode Aurora Mode NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Sprite Burst Mode Highest temporal resolution Frame interval as low as 1 ms Frame interval largely set by exposure duration, EXP = 1~100ms Triggered by event, take N images, N<12 Images stacked in CCD vertical storage register Readout of data after image acquisition Data stored in memory Dead time between events Dead time during image readout Dead time can be minimized by changing N NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Sprite Burst Mode Timing Tframe N • Tframe Begin acquisition of N images at leading edge of Event Trigger Treadout Image readout time ~ N • Treadout NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Sprite Burst Mode Event Timing Tframe Period of one Sprite frame depends on Exposure duration, EXP EXP can vary from 1 ~ 100 ms Treadout Time to readout one frame For Fvertical = 500 kHz and Fhorizontal = 8 MHz Treadout ~ 6 ms No Image Acquisition during readout Dead time ~ N • Treadout , where N = number of images acquired NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Sprite Continuous Mode CCD camera is continuously taking images Image data is readout simultaneously with each image exposure Exposure duration of 1~100 ms Image data is continuously stored in Memory circular buffer Event trigger simply causes a new buffer allocation No Dead Time between events But temporal resolution reduced to ~ 6 ms NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Sprite Continuous Mode Clocking Image Area Storage Area Expose Image AND Shift & Read image from Storage Area Shift Image & Storage Areas Transferanother image into Storage Area Repeat Cycle Note: Storage area is shifted twice as often NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Sprite Continuous Mode Timing Tframe Event occurs Data for that event starts on 8th frame afterwards 9 · Tframe First frame of event available in memory NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Continuous Mode Event Timing Tframe Period of one Sprite frame depends on Exposure duration, EXP, and the time to readout one frame, whichever is longer For Fvertical = 500 kHz and Fhorizontal = 8 MHz minimum Tframe ~ 6 ms Tframe could be longer if EXP > frame readout period EXP can be < Tframe , since we use gating to control exposure NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Aurora Mode Imaging The time to shift and readout one image: ~9 ms Read out image Shift image entire vertical register Take exposure The time to shift and readout one image: ~9 ms Exposure duration can be as long as ~ 1 second NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Imager Mechanical Layout NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Imager Mechanical Layout con’t NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Front End Electronics Block Diagram Correlated Double Sample A/D Converters Clock Drivers: Analog SPDT Switches R/C waveform shaping Digital I/O Timing Generator Based on FPGA CCD Preamps Develops Bias & Clock Voltages Linear Regulators Voltage Monitor NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Front End Electronics Interface Data[0..11] 12 bits per pixel PixelClock pixel data strobe FrameClock start of frame signal Acquire signals start of exposure in Aurora mode signals Event in Sprite mode CommandData serial data interface for upload of camera parameters VoltageMonitor switched analog output Power dc voltages NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Auxiliary Electronics Interface Thermistors TEC hot side Lens Filter Wheel Filter Motor Heater Circuits Photocathode PS On/off control Gated TEC Power Supply On/off control Sun Sensor Analog output Filter Wheel Motor Stepper motor (4 phases) NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000

Principal Camera Parameters Gated operation enable Photocathode gate open/close Sprite Burst Mode enable Set Burst mode number of images, N Sprite Continuous Mode enable Aurora Mode enable Dark image acquire Set Exposure (EXP) duration Set repetition (REPTIME) period NCKU UCB Tohoku Sprite Imager S. Harris SDR 7 Jun 2000